In order to make a doubled yarn of the above-described general type it is standard practice to feed the core yarn axially through the hollow spindle of a spinning device carrying the winder yarn, so that the winder yarn is wound around the core yarn. Normally the core yarn is drafted immediately upstream of the winding location by passing it through sets of rollers rotating at peripheral speeds increasing in the travel direction.
In order to prevent loosened fibers from escaping into the air where they can foul equipment and present a health hazard for workers, it is known to create an axial air current through the spindle. Thus the loosened fibers can be sucked up and carried away. This procedure is also employed to lay loose fibers parallel to the core yarn so that they can be caught under the winder yarn. To this end the spacing between the nip of the last pair of drafting rollers engaging the core yarn and the intake end of the hollow spindle must be smaller than the average fiber length of the core yarn.
The main problem with this type of system is that it is difficult to combine it with an automatic yarn-breakage detector and yarn-trapping device. The small distance between the furthest downstream pair of drafting rollers and the winding location makes it impossible to mount the yarn-trapper in this region. The lint- or fiber-catching air stream cannot itself be employed to aspirate the broken yarn, since the winder-yarn package must be lifted off to rethread the machine.
It is also known to provide on a spinning machine a suction cap which is supported by means of fork-shaped projections on the upper roller of the output rollers. A suction tube is connected to this cap to aspirate loose fibers. Such an arrangement is not usable on the above-described type of drafting/doubling apparatus because too many fibers can work loose between the cap and the winding location.